The usual home-type sky-light dome unit is paired with a ceiling window positioned below the dome, and spaced therefrom a few feet (the height of the attic or under-roof airspace). The space between the sky-light dome and the ceiling window is usually enclosed by a custom-built (and thus expensive) box or shaft, which is needed for thermal insulation and for excluding insects and dust. It is the principal object of this invention to provide a simple, inexpensive, easily installed, yet highly effective sky-light shaft formed of a section of a flexible tubing. Other objects and advantages will appear as the following detailed description proceeds.